# PR draft: fix(kompress): load merged.pt for the v2 checkpoint instead of the unmerged PEFT safetensors Branch: `rnoz/fix-kompress-merged-checkpoint` (off `upstream/main`). Two commits. Issue: https://github.com/headroomlabs-ai/headroom/issues/2714 (filed, open). --- ## Description `_load_kompress_pytorch` in `headroom/transforms/kompress_compressor.py` downloaded `model.safetensors` from the default model repo `chopratejas/kompress-v2-base` and loaded it with `strict=False`, discarding the missing/unexpected key report. That file is the unmerged PEFT checkpoint (encoder keys prefixed `encoder.base_model.model...`), which never matches `HeadroomCompressorModel`'s plain `encoder.*` keys. The LoRA-adapted encoder weights were silently dropped while `token_head`/`span_conv` happened to match and loaded fine, so the model ran with a stock, non-adapted `answerdotai/ModernBERT-base` encoder feeding correctly trained decision heads, with no error and a healthy status reported everywhere. `scripts/export_kompress_v2_onnx.py` already documents this exact mismatch and loads the correct `merged.pt` sub-state-dicts for its own export path. This PR mirrors that same loading logic into the runtime PyTorch loader, with a fallback to the plain `model.safetensors` format for repos that never shipped a `merged.pt` (verified against the v1 `chopratejas/kompress-base` repo via the public HF API, which has no `merged.pt`). Both paths now check the missing/unexpected key report and raise instead of silently proceeding on a mismatch. A second commit fixes a gap an adversarial review caught in the first: the cache-only (`allow_download=False`, startup preload) path could not tell "this repo genuinely has no merged.pt" apart from "merged.pt exists but is not downloaded yet", so it would have fallen back to a stale `model.safetensors` left over from before this fix on exactly the upgrade path this PR is meant to close. It now uses `huggingface_hub`'s own `.no_exist` cache marker (via a new `hf_entry_known_absent()` helper in `headroom/onnx_runtime.py`) to make that distinction without a network call, and only falls back when absence is confirmed; otherwise it raises `KompressModelNotCached` so the caller defers instead of guessing. Closes #2714 ## Type of Change - [x] Bug fix (non-breaking change that fixes an issue) ## Changes Made - `headroom/transforms/kompress_compressor.py`: added `_load_merged_state_dict`, `_load_plain_state_dict`, and `_load_pytorch_weights`, replacing the inline `model.safetensors` download + `load_state_dict(strict=False)` call in `_load_kompress_pytorch`. `merged.pt` is tried first; the plain format is only used when its absence is confirmed. - `headroom/onnx_runtime.py`: added `hf_entry_known_absent()`, a thin wrapper around `huggingface_hub.try_to_load_from_cache()` that reads the on-disk `.no_exist` marker HF writes after a real 404, so cache-only code can distinguish "confirmed absent" from "never checked" without hitting the network. - `tests/test_transforms/test_kompress_compressor.py`: added `TestPytorchWeightLoading` (8 tests) covering the merged-checkpoint happy path, missing-section and key-mismatch failures, the plain-format fallback for repos without `merged.pt`, and the cache-only ambiguity fix (confirmed-absent vs unconfirmed). ## Testing - [x] Unit tests pass (`pytest`) - [x] Linting passes (`ruff check`) - [x] Type checking passes (`mypy`) - [x] Manual testing performed (real download against the live `chopratejas/kompress-v2-base` repo, not just mocks) ### Test Output ```text $ .venv/bin/python3 -m pytest tests/ -k kompress -q 178 passed, 7 skipped in 22.39s $ .venv/bin/python3 -m ruff check headroom/onnx_runtime.py headroom/transforms/kompress_compressor.py tests/test_transforms/test_kompress_compressor.py All checks passed! $ .venv/bin/python3 -m ruff format --check headroom/onnx_runtime.py headroom/transforms/kompress_compressor.py tests/test_transforms/test_kompress_compressor.py 3 files already formatted $ .venv/bin/python3 -m mypy headroom/onnx_runtime.py headroom/transforms/kompress_compressor.py Success: no issues found in 2 source files ``` ## Real Behavior Proof Ran the actual fixed loader against the live `chopratejas/kompress-v2-base` HF repo (not a mock), before and after each fix: ```text # BEFORE (parsed the real cached model.safetensors header by hand, no safetensors lib needed): total tensors: 316 encoder.base_model.model.embeddings.norm.weight encoder.base_model.model.embeddings.tok_embeddings.weight ...(all 310 encoder tensors share this prefix)... span_conv.0.bias / span_conv.0.weight / span_conv.2.bias / span_conv.2.weight token_head.bias / token_head.weight exact prefix match count with plain "encoder.<rest>": 0 # This confirms the pre-fix code's model.load_state_dict(state_dict, strict=False) # silently dropped every encoder weight (0 keys match HeadroomCompressorModel.encoder), # while token_head/span_conv happened to match and loaded. # AFTER (commit 1, real merged.pt download + load): $ .venv/bin/python3 -c " import headroom.transforms.kompress_compressor as kmod model = kmod._get_model_class()() kmod._load_pytorch_weights(model, 'chopratejas/kompress-v2-base', allow_download=True) print('SUCCESS: 0 missing/unexpected keys across all three sections') " SUCCESS: 0 missing/unexpected keys across all three sections # AFTER (full pipeline, real end-to-end compression through the public API): $ .venv/bin/python3 -c " import headroom.transforms.kompress_compressor as kmod compressor = kmod.KompressCompressor() result = compressor.compress(sample_traceback_plus_boilerplate_text) print(result.original_tokens, result.compressed_tokens, result.tokens_saved) print('ValueError: bad input' in result.compressed) " 497 454 43 True # must-keep line (the actual error) survived compression # AFTER (commit 2, cache-only ambiguity): unit tests # test_cache_only_defers_instead_of_using_stale_plain_checkpoint: PASSED # test_cache_only_uses_plain_checkpoint_when_merged_pt_confirmed_absent: PASSED ``` ## Review Readiness - [x] I have performed a self-review - [x] An independent adversarial review pass was run on both commits before this PR was opened; its one finding (the cache-only ambiguity) is fixed in commit 2, verified with new regression tests - [x] This PR is ready for human review ## Checklist - [x] My code follows the project's style guidelines - [x] I have performed a self-review of my code - [x] I have commented my code, particularly in hard-to-understand areas - [ ] I have made corresponding changes to the documentation (N/A: internal loader behavior, no public API or config surface changed) - [x] My changes generate no new warnings - [x] I have added tests that prove my fix is effective (regression tests for both the original silent-drop bug and the cache-only ambiguity found in review) - [x] New and existing unit tests pass locally with my changes - [x] I did not edit `CHANGELOG.md` ## Additional Notes - Both `merged.pt` and the plain `model.safetensors` fallback now raise loudly on any state-dict mismatch instead of proceeding with partially-loaded weights, closing the general silent-failure class this bug belonged to, not just this one instance of it. - No other call sites of `_load_kompress_pytorch` or its removed inline code exist; its public signature is unchanged. |
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| .codegraph | ||
| .devcontainer | ||
| .github | ||
| .serena | ||
| benchmarks | ||
| crates | ||
| docker | ||
| docs | ||
| e2e | ||
| examples | ||
| headroom | ||
| plugins | ||
| REALIGNMENT | ||
| sbom | ||
| scripts | ||
| sdk/typescript | ||
| sql | ||
| tests | ||
| wiki | ||
| .actrc | ||
| .actrc.local.example | ||
| .changelog.md | ||
| .commitlintrc.json | ||
| .dockerignore | ||
| .env.act.example | ||
| .env.example | ||
| .git-blame-ignore-revs | ||
| .gitattributes | ||
| .gitguardian.yaml | ||
| .gitignore | ||
| .gitleaks.toml | ||
| .pre-commit-config.yaml | ||
| .release-please-config.json | ||
| .release-please-manifest.json | ||
| .releasemetadata | ||
| Cargo.lock | ||
| Cargo.toml | ||
| CHANGELOG.md | ||
| claude_analysis_ttl.py | ||
| CODE_OF_CONDUCT.md | ||
| codecov.yml | ||
| CONTRIBUTING.md | ||
| deny.toml | ||
| docker-bake.hcl | ||
| docker-compose.yml | ||
| Dockerfile | ||
| Headroom-2.gif | ||
| headroom-savings.png | ||
| headroom_learn.gif | ||
| HeadroomDemo-Fast.gif | ||
| LICENSE | ||
| llms.txt | ||
| Makefile | ||
| mkdocs.yml | ||
| NOTICE | ||
| pyproject.toml | ||
| README.md | ||
| rust-toolchain.toml | ||
| RUST_DEV.md | ||
| SECURITY.md | ||
| server.json | ||
| TESTING-copilot-subscription.md | ||
| uv.lock | ||
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The context compression layer for AI agents
60–95% fewer tokens (for JSON data), 15-20% fewer tokens (for coding agents) · library · proxy · MCP · content-aware compressors · local-first · reversible
Docs · Install · Proof · Agents · Discord · llms.txt
AI agents / LLMs: read /llms.txt here, or fetch the live index / full docs blob.
Headroom compresses everything your AI agent reads — tool outputs, logs, RAG chunks, files, and conversation history — before it reaches the LLM. Same answers, fraction of the tokens.
Live: 10,144 → 1,260 tokens — same FATAL found.
What it does
- Library —
compress(messages)in Python or TypeScript, inline in any app - Proxy —
headroom proxy --port 8787, zero code changes, any language - Agent wrap —
headroom wrap claude|codex|grok|copilot|cursor|aider|opencode|cline|continue|goose|openhands|openclaw|vibe|omp|zcodein one command; undo withheadroom unwrap <tool> - MCP server —
headroom_compress,headroom_retrieve,headroom_statsfor any MCP client - Cross-agent memory — shared store across Claude, Codex, Gemini, Grok, auto-dedup
headroom learn— mines failed sessions, writes corrections toCLAUDE.local.md(default, gitignored) orCLAUDE.md/AGENTS.md/GEMINI.md/GROK.md- Output token reduction — trims what the model writes back (not just what you send): drops ceremony/restated code and skips deep "thinking" on routine steps. See Output token reduction.
- Reversible (CCR) — originals are cached for retrieval on demand
How it works (30 seconds)
Your agent / app
(Claude Code, Cursor, Codex, LangChain, Agno, Strands, your own code…)
│ prompts · tool outputs · logs · RAG results · files
▼
┌────────────────────────────────────────────────────┐
│ Headroom (runs locally — your data stays here) │
│ ──────────────────────────────────────────────── │
│ CacheAligner → ContentRouter → CCR │
│ ├─ SmartCrusher (JSON) │
│ ├─ CodeCompressor (AST) │
│ └─ Kompress-v2-base (text, HF) │
│ │
│ Cross-agent memory · headroom learn · MCP │
└────────────────────────────────────────────────────┘
│ compressed prompt + retrieval tool
▼
LLM provider (Anthropic · OpenAI · Bedrock · …)
- ContentRouter — detects content type, selects the right compressor
- SmartCrusher / CodeCompressor / Kompress-v2-base — compress JSON, AST, or prose
- CacheAligner - detects and warns about volatile content that can bust provider KV cache prefixes; never rewrites prompts
- CCR — stores originals locally; LLM calls
headroom_retrieveif it needs them
→ Architecture · CCR reversible compression · Kompress-v2-base model card
Get started (60 seconds)
# 1 — Install
uv tool install --python 3.13 "headroom-ai[all]" # CLI as a global tool in a self-contained virtual env
pip install "headroom-ai[all]" # Python — ships the `headroom` CLI
npm install headroom-ai # TypeScript SDK only — no `headroom` CLI
# 2 — Pick your mode (the `headroom` commands below come from the uv or pip install)
headroom deploy # turnkey local deployment + agent config
headroom wrap claude # wrap a coding agent
headroom proxy --port 8787 # drop-in proxy, zero code changes
# or: from headroom import compress # inline library
# 3 — Verify setup and see the savings
headroom doctor # health check — confirms routing is working
headroom perf
headroom dashboard # live savings dashboard (proxy must be running)
To use headroom, it is recommended you launch a wrapped agent session each time so that all necessary setup is completed. When wrapping a coding agent, headroom starts a local proxy, installs Serena for semantic code navigation, and launches a coding agent session configured to proxy requests through headroom.
The headroom CLI ships only via the PyPI package. The npm headroom-ai is the TypeScript SDK — a library you import (import { compress } from 'headroom-ai'), not a CLI, so it provides no headroom command.
Granular extras: [proxy], [mcp], [ml], [code], [memory], [vector] (optional HNSW backend — needs a C++ toolchain, not in [all]), [relevance], [image], [agno], [langchain], [evals], [pytorch-mps] (Apple-GPU memory-embedder offload — set HEADROOM_EMBEDDER_RUNTIME=pytorch_mps). Requires Python 3.10+.
Codex / global install
If Codex or another MCP client cannot inherit a shell PATH reliably, install Headroom as a persistent uv tool and point the client at the absolute binary path:
uv tool install "headroom-ai[all]"
command -v headroom
Then use the returned path in MCP config:
[mcp_servers.headroom]
command = "/absolute/path/from/command-v/headroom"
args = ["mcp", "serve"]
command = "headroom" only works when the client starts with a PATH that already includes the uv tool directory.
Proof
Savings on real agent workloads:
| Workload | Before | After | Savings |
|---|---|---|---|
| Code search (100 results) | 17,765 | 1,408 | 92% |
| SRE incident debugging | 65,694 | 5,118 | 92% |
| GitHub issue triage | 54,174 | 14,761 | 73% |
| Codebase exploration | 78,502 | 41,254 | 47% |
Accuracy preserved on standard benchmarks:
| Benchmark | Category | N | Baseline | Headroom | Delta |
|---|---|---|---|---|---|
| GSM8K | Math | 100 | 0.870 | 0.870 | ±0.000 |
| TruthfulQA | Factual | 100 | 0.530 | 0.560 | +0.030 |
| SQuAD v2 | QA | 100 | — | 97% | 19% compression |
| BFCL | Tools | 100 | — | 97% | 32% compression |
Reproduce: python -m headroom.evals suite --tier 1 · Full benchmarks & methodology
Output token reduction (cut what the model writes back)
Everything above shrinks the prompt you send. But you also pay for every token the model writes back — and on Opus-class models output costs 5× input. A lot of that output is waste: "Great, let me…" preambles, re-printing code you just showed it, and deep "thinking" on routine steps like reading a file.
Headroom can trim that too, from the proxy, without you changing any code:
- Verbosity steering — appends a short "be terse, don't restate context" note to the end of the system prompt (so your prompt cache still hits).
- Effort routing — when a turn is just the model resuming after a tool result (a file read, a passing test), it dials the model's thinking effort down. New questions and errors keep full effort.
Applies to Anthropic /v1/messages and OpenAI-compatible endpoints
(/v1/chat/completions, /v1/responses). Effort routing uses
reasoning_effort on OpenAI, thinking.budget_tokens /
output_config.effort on Anthropic — same clamp-only invariant on both
paths, same output_shaper:* label vocabulary.
Turn it on:
export HEADROOM_OUTPUT_SHAPER=1 # off by default
headroom proxy --port 8787
Already running a proxy? These switches are read live on every request, so a proxy that
headroom wrapreused (rather than started) would not see a value you export afterwards — its environment was snapshotted at launch.headroom wrapnow hot-syncs your current settings to the running proxy via a loopbackPOST /admin/runtime-env, so they take effect immediately with no restart (no cold start, no dropped requests, no lost caches). Set them before youwrap. On a shared proxy these overrides are global — the last explicit setting wins.
Learn the right terseness for you. People don't say how terse they want
answers — they show it (they interrupt long replies, or move on before they
could have read them). headroom learn --verbosity reads your past sessions and
picks the level automatically:
headroom learn --verbosity # preview what it found (dry run)
headroom learn --verbosity --apply # save it; the proxy uses it from now on
See how many output tokens you saved. Output savings are counterfactual — we never see what the model would have written — so Headroom reports an honest estimate with a confidence range, never a made-up number:
headroom output-savings
# Reduction: 31.7% (95% CI 27.7% … 35.7%) [estimated]
Want a measured number instead of an estimate? Leave 10% of conversations
unshaped as a control group: export HEADROOM_OUTPUT_HOLDOUT=0.1. The dashboard
shows an Output Tokens Saved card next to input compression, labelled
measured or estimated with the confidence band.
→ Full write-up incl. the measurement methodology: Output token reduction
Agent compatibility matrix
| Agent | headroom wrap |
Notes |
|---|---|---|
| Claude Code | ✅ | --memory · --code-graph · --1m · --tool-search |
| Codex | ✅ | shares memory with Claude |
| Grok CLI | ✅ | routes via GROK_MODELS_BASE_URL |
| Cursor | Manual setup | starts proxy and prints base URLs for Cursor settings |
| Aider | ✅ | starts proxy + launches |
| Copilot CLI | ✅ | starts proxy + launches |
| OpenClaw | ✅ | installs as ContextEngine plugin |
| OpenCode | ✅ | injects config · starts proxy + launches |
| Cline | ✅ | starts proxy + injects config |
| Continue | ✅ | starts proxy + injects config |
| Goose | ✅ | starts proxy + launches |
| OpenHands | ✅ | starts proxy + launches |
| Mistral Vibe | ✅ | starts proxy + launches |
| Oh My Pi | ✅ | injects config · starts proxy + launches |
| Cortex Code | Library only | 60–65% savings (library mode; no wrap) |
| Kimi CLI | ✅ | OAuth bearer forwarded — log in once |
| ZCode | ✅ | starts proxy and prints base URLs for ZCode settings |
Any OpenAI-compatible client works via headroom proxy. MCP-native: headroom mcp install.
Undo durable wrapping with headroom unwrap <tool> (supports: claude, copilot, codex, grok, kimi, omp, opencode, openclaw, zcode).
Registry authors can use the canonical server.json in the repo root instead of reconstructing the headroom mcp serve contract from prose.
GitHub Copilot CLI subscription mode
Headroom can route GitHub Copilot CLI subscription traffic through the local proxy:
headroom copilot-auth login
headroom wrap copilot --subscription -- --model gpt-4o
This lets Headroom intercept OpenAI-compatible Copilot CLI requests and apply the same proxy compression pipeline before forwarding to GitHub Copilot's hosted API. The wrapper exchanges Headroom's reusable GitHub OAuth token for Copilot's short-lived API token and prints the upstream endpoint as COPILOT_PROVIDER_API_URL=... during launch.
headroom copilot-auth login stores a Headroom-specific Copilot OAuth token.
This avoids relying on generic GitHub or Copilot CLI tokens that can read
Copilot account metadata but may still be rejected by Copilot's token-exchange
endpoint.
For GitHub Enterprise Server or custom-domain Copilot deployments, set one of these before launching:
export GITHUB_COPILOT_ENTERPRISE_DOMAIN=ghe.example.com
# or
export GITHUB_COPILOT_ENTERPRISE_URL=https://ghe.example.com
Both variables are supported. If both are set,
GITHUB_COPILOT_ENTERPRISE_URL takes precedence.
For GitHub.com Enterprise Cloud URLs such as
github.com/enterprises/your-enterprise, do not set an enterprise-domain
override. Headroom uses GitHub's normal token-exchange endpoint and the Copilot
API endpoint advertised for the signed-in account.
Platform support note: macOS auth reuse via Copilot CLI Keychain storage has been smoke-tested. Windows Credential Manager, Linux Secret Service / secret-tool, and Docker/CI token-injection paths are implemented or planned as auth-discovery paths, but still need real OS validation before they should be considered fully vetted. For Docker and CI, prefer passing an explicit GITHUB_COPILOT_TOKEN or GITHUB_COPILOT_GITHUB_TOKEN rather than relying on host keychain access.
When to use · When to skip
Great fit if you…
- run AI coding agents daily and want savings without changing your code
- work across multiple agents and want shared memory
- need reversible compression — originals are retrievable via CCR within the configured TTL
Skip it if you…
- only use a single provider's native compaction and don't need cross-agent memory
- work in a sandboxed environment where local processes can't run
Integrations — drop Headroom into any stack
| Your setup | Hook in with |
|---|---|
| Any Python app | compress(messages, model=…) |
| Any TypeScript app | await compress(messages, { model }) |
| Anthropic / OpenAI SDK | withHeadroom(new Anthropic()) · withHeadroom(new OpenAI()) |
| Vercel AI SDK | wrapLanguageModel({ model, middleware: headroomMiddleware() }) |
| LiteLLM | litellm.callbacks = [HeadroomCallback()] |
| LangChain | HeadroomChatModel(your_llm) |
| Agno | HeadroomAgnoModel(your_model) |
| Strands | Strands guide |
| ASGI apps | app.add_middleware(CompressionMiddleware) |
| Multi-agent | SharedContext().put / .get |
| MCP clients | headroom mcp install |
What's inside
- SmartCrusher — universal JSON: arrays of dicts, nested objects, mixed types.
- CodeCompressor — AST-aware for Python, JS/TS, Go, Rust, Java, C/C++, Perl.
- Kompress-v2-base — our HuggingFace model, trained on agentic traces.
- Image compression — 40–90% reduction via trained ML router.
- CacheAligner - detects and warns about volatile content that can bust provider KV cache prefixes; never rewrites prompts.
- Live-zone compression — compresses only new bytes (fresh tool output, latest turn); frozen prefix stays byte-identical so provider cache is not busted. History is never dropped.
- CCR — reversible compression; LLM retrieves originals on demand.
- Cross-agent memory — shared store, agent provenance, auto-dedup.
- SharedContext — compressed context passing across multi-agent workflows.
headroom learn— plugin-based failure mining for Claude, Codex, Gemini.
Pipeline internals
Headroom exposes one stable request lifecycle across compress(), the SDK, and the proxy:
Setup → Pre-Start → Post-Start → Input Received → Input Cached → Input Routed → Input Compressed → Input Remembered → Pre-Send → Post-Send → Response Received
- Transforms do the work: CacheAligner → ContentRouter → SmartCrusher / CodeCompressor / Kompress-base (live-zone only; IntelligentContext and RollingWindow were retired in PR-B1).
- Pipeline extensions observe or customize lifecycle stages via
on_pipeline_event(...). - Compression hooks sit alongside the canonical lifecycle as an additional extension seam.
- Proxy extensions remain the server/app integration seam for ASGI middleware, routes, and startup policy.
Provider and tool-specific behavior lives under headroom/providers/ so core orchestration stays focused on lifecycle, sequencing, and policy.
- CLI/tool slices:
headroom/providers/claude,copilot,codex,grok,openclaw - Provider runtime slices:
headroom/providers/claude,gemini, plus shared backend/runtime dispatch inheadroom/providers/registry.py - Core files stay orchestration-first:
wrap.py,client.py,cli/proxy.py, andproxy/server.pydelegate provider-specific env shaping, API target normalization, backend selection, and transport dispatch.
Headroom for teams
Headroom OSS is built for individual developers: run headroom proxy or headroom wrap on your laptop and start cutting tokens in minutes — free, local-first, your data never leaves your machine.
Running it across a whole engineering org is a different job: a shared, always-on deployment; centralized config and version rollout; org-wide savings dashboards; SSO and access controls; air-gapped / VPC installs; and someone to call when it matters. That's what we help companies with — self-hosted with support, or fully managed.
If your team is spending real money on LLM tokens — Claude Code, Codex, Cursor, or agents running in CI — and you want those savings across everyone, not just one laptop:
→ Email hello@headroomlabs.ai with your stack and rough monthly LLM spend, and we'll help you roll Headroom out across your organization.
Everything in this repo stays open source (Apache 2.0). The managed offering is simply for teams that would rather have it deployed, supported, and scaled for them.
Install
uv tool install --python 3.13 "headroom-ai[all]" # CLI, isolated app env
pip install "headroom-ai[all]" # Python, everything — includes the `headroom` CLI
npm install headroom-ai # TypeScript SDK (library only — no `headroom` CLI)
docker pull ghcr.io/chopratejas/headroom:latest
Granular extras: [proxy], [mcp], [ml] (Kompress-v2-base), [code], [memory], [vector] (optional HNSW backend — needs a C++ toolchain, not in [all]), [relevance], [image], [agno], [langchain], [evals], [pytorch-mps] (Apple-GPU memory-embedder offload — set HEADROOM_EMBEDDER_RUNTIME=pytorch_mps). Requires Python 3.10+.
Note
:
[all]covers the core stack but excludes framework adapters. Install them separately:pip install "headroom-ai[langchain]"(also[agno],[strands],[anyllm],[bedrock]).
Using uv for the headroom CLI? Prefer uv tool install so the command lives in an isolated app environment. On macOS, pass --python 3.13 if your default python3 is newer than the current wheel set:
brew install python@3.13 # if Python 3.13 is not already available
uv tool install --python 3.13 "headroom-ai[all]"
uv tool update-shell # if ~/.local/bin is not already on PATH
headroom --version
For MCP clients such as Codex that do not inherit your interactive shell PATH, configure the absolute executable path returned by command -v headroom:
[mcp_servers.headroom]
command = "/Users/you/.local/bin/headroom"
args = ["mcp", "serve"]
Current native wheels cover macOS Apple Silicon and Linux. On Intel macOS, use Docker-native install until native wheel support lands.
Using pipx? Choose a supported interpreter explicitly:
pipx install --python python3.13 "headroom-ai[all]"
Pick 3.13 if you want dollar savings. The dashboard's Proxy $ Saved tile prices compression with LiteLLM, and LiteLLM can't be installed on Python 3.14+. On 3.14 token savings still track, but the dollar figure stays
$0.00. If you already installed on 3.14, switch withpipx reinstall headroom-ai --python python3.13and restart the proxy.
→ Installation guide — Docker tags, persistent service, PowerShell, devcontainers.
CPU requirement (x86/x86_64): the ONNX-backed features — Magika content detection and embedding relevance — use a precompiled ONNX Runtime that needs AVX2. On x86 hosts without AVX2 (some Docker/QEMU setups and older cloud VMs) Headroom automatically falls back to its non-ONNX paths (BM25 relevance, heuristic detection) rather than crashing.
arm64/Apple Silicon needs no AVX2.
Updating
headroom update # detects pip / pipx / uv tool and upgrades in place
headroom update --check # report the latest release without upgrading
headroom update --pre # include pre-releases
headroom update figures out how Headroom was installed (pip/venv, pip --user,
pipx, uv tool) and runs the matching upgrade across macOS, Linux, and Windows.
For git checkouts, editable installs, Docker images, and externally-managed
system Pythons (PEP 668) it prints the correct manual step instead of guessing.
The proxy also shows a one-line "update available" notice on startup. It checks
PyPI at most once a day, in the background, and never blocks. Opt out with
HEADROOM_UPDATE_CHECK=off (also skipped in --stateless mode and CI).
Corporate / SSL-inspection environments
If pip install "headroom-ai[all]" fails with CERTIFICATE_VERIFY_FAILED
(unable to get local issuer certificate), your network uses SSL inspection — a MITM
proxy presenting a company-issued CA. The build backend (maturin) downloads rustup over a
connection your TLS stack doesn't trust. Install Rust first so the build doesn't fetch it:
# macOS / Linux
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh && rustup default stable
# Windows
winget install Rustlang.Rustup && rustup default stable
Restart your shell, then pip install "headroom-ai[all]". A prebuilt wheel avoids the Rust
build entirely where available: pip install --only-binary headroom-ai headroom-ai. Prebuilt
wheels are published for Windows (win_amd64), Linux (x86_64 / aarch64), and macOS
(Apple Silicon and Intel), so installs on those platforms never need a local Rust toolchain — the
Rust-first dance above is only for the platform-independent sdist fallback when no wheel matches.
Two runtime assets are fetched over TLS; if they are blocked, trust your corporate CA via
REQUESTS_CA_BUNDLE / SSL_CERT_FILE / CURL_CA_BUNDLE:
cdn.pyke.io— the ONNX Runtime for the Rust core. Alternatively pre-provide it withORT_STRATEGY=systemandORT_LIB_LOCATION=/path/to/onnxruntime.huggingface.co— thekompress-basecompression model. Pre-download it and run withHF_HUB_OFFLINE=1, or setHF_ENDPOINTto a trusted mirror.
Running with compression disabled (pure gateway) requires neither asset.
Intel macOS (x86_64-apple-darwin): no prebuilt ONNX Runtime binary (#941)
ort-sys ships no prebuilt ONNX Runtime binary for Intel macOS, so a source
build fails by default even outside a corporate-proxy environment. The same
ORT_STRATEGY=system mechanism above fixes it — point it at a system ONNX
Runtime instead:
brew install onnxruntime
ORT_STRATEGY=system \
ORT_LIB_LOCATION="$(brew --prefix onnxruntime)/lib" \
ORT_PREFER_DYNAMIC_LINK=1 \
pip install "headroom-ai[all]"
# ORT is dlopen'd at runtime too:
export ORT_DYLIB_PATH="$(brew --prefix onnxruntime)/lib/libonnxruntime.dylib"
ORT_LIB_LOCATION must point at lib/ (not the bare prefix) and
ORT_PREFER_DYNAMIC_LINK=1 is required, or ORT_STRATEGY=system still
attempts static linking, which the Homebrew keg doesn't provide.
"Basic Constraints of CA cert not marked critical" (Python 3.13+ strict mode)
A different failure from the one above. If TLS fails with:
[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed:
Basic Constraints of CA cert not marked critical
then the corporate CA is found and trusted — adding it to a CA bundle changes nothing.
Python 3.13 + OpenSSL 3.x enable VERIFY_X509_STRICT by default, which enforces RFC 5280
§4.2.1.9: a CA cert's basicConstraints must be marked critical. Inspection roots like
Zscaler set CA:TRUE without the critical bit, so the chain is rejected.
Set HEADROOM_TLS_STRICT=0 to clear only the strict flag from every TLS context
Headroom controls — the proxy's httpx upstream client and the urllib3/huggingface_hub
path used for model downloads. Chain validation, signature, expiry, and hostname checks all
stay on; this is strictly narrower than disabling verification.
HEADROOM_TLS_STRICT=0 headroom proxy --port 8787
The Rust core's ONNX download (cdn.pyke.io) uses a separate TLS stack (rustls / OS trust
store), unaffected by HEADROOM_TLS_STRICT. On Windows the corporate root must be in the
machine certificate store (browsers already trust it there); or pre-provision ONNX
Runtime with ORT_STRATEGY=system + ORT_LIB_LOCATION=/path/to/onnxruntime to skip the
download entirely.
headroom learn
headroom learn — mines failed sessions, writes corrections to CLAUDE.local.md (default, gitignored; use --target CLAUDE.md for the shared team file) / AGENTS.md / GEMINI.md.
Documentation
| Start here | Go deeper |
|---|---|
| Quickstart | Architecture |
| Proxy | How compression works |
| MCP tools | CCR — reversible compression |
| Memory | Cache optimization |
| Failure learning | Benchmarks |
| Configuration | Limitations |
Persistent installs (headroom init / headroom install apply) |
Savings analytics (headroom savings / headroom perf / headroom doctor) |
Compared to
Headroom runs locally, covers every content type, works with every major framework, and is reversible.
| Scope | Deploy | Local | Reversible | |
|---|---|---|---|---|
| Headroom | All context — tools, RAG, logs, files, history | Proxy · library · middleware · MCP | Yes | Yes |
| Compresr, Token Co. | Text sent to their API | Hosted API call | No | No |
| OpenAI Compaction | Conversation history | Provider-native | No | No |
Stack & integrations. Headroom is the proxy — that's what we build and offer, and it compresses everything flowing through it no matter what sits upstream. Our recommended companion is Serena (installed by default when you wrap an agent) for semantic code navigation — plus Ponytail if you want leaner model output. Everything else is your call: you're free to attach your own tooling — code-memory MCP, Graphify, Caveman, or any MCP server — and Headroom compresses downstream of all of it.
Contributing
git clone https://github.com/chopratejas/headroom.git && cd headroom
uv sync --extra dev && uv run pytest
Devcontainers in .devcontainer/ (default + memory-stack with Qdrant & Neo4j). See CONTRIBUTING.md.
Community
- Discord — questions, feedback, war stories.
- Kompress-v2-base on HuggingFace — the model behind our text compression.
Community projects
- Claude Code status-line indicator — a Claude Code plugin that shows live Headroom usage in your status line: idle until
headroom_compressfires, then the running total of tokens saved.
License
Apache 2.0 — see LICENSE.